Simple proton spectroscopic imaging.

Dixon, William J.

doi:10.1148/radiology.153.1.6089263

Cited by 1,973 publications

(1,395 citation statements)

References 0 publications

Supporting

Mentioning

1,369

Contrasting

Unclassified

Order By: Relevance

“…MR liver signal to noise ratio (SNR) was measured before and 25 minutes after Gd‐Hyd injection, and the relative increase in SNR was computed (% Δ SNR) 28. A 2‐point Dixon sequence was used to estimate liver fat content 29. Imaging parameters can be found in the http://onlinelibrary.wiley.com/doi/10.1002/hep4.1193/full.…”

Section: Methodsmentioning

confidence: 99%

Molecular magnetic resonance imaging accurately measures the antifibrotic effect of EDP‐305, a novel farnesoid X receptor agonist

Erstad

Farrar

Ghoshal

et al. 2018

Hepatology Communications

View full text Add to dashboard Cite

We examined a novel farnesoid X receptor agonist, EDP‐305, for its antifibrotic effect in bile duct ligation (BDL) and choline‐deficient, L‐amino acid‐defined, high‐fat diet (CDAHFD) models of hepatic injury. We used molecular magnetic resonance imaging with the type 1 collagen‐binding probe EP‐3533 and the oxidized collagen‐specific probe gadolinium hydrazide to noninvasively measure treatment response. BDL rats (n = 8 for each group) were treated with either low or high doses of EDP‐305 starting on day 4 after BDL and were imaged on day 18. CDAHFD mice (n = 8 for each group) were treated starting at 6 weeks after the diet and were imaged at 12 weeks. Liver tissue was subjected to pathologic and morphometric scoring of fibrosis, hydroxyproline quantitation, and determination of fibrogenic messenger RNA expression. High‐dose EDP‐305 (30 mg/kg) reduced liver fibrosis in both the BDL and CDAHFD models as measured by collagen proportional area, hydroxyproline analysis, and fibrogenic gene expression (all P < 0.05). Magnetic resonance signal intensity with both EP‐3533 in the BDL model and gadolinium hydrazide in the CDAHFD model was reduced with EDP‐305 30 mg/kg treatment (P < 0.01). Histologically, EDP‐305 30 mg/kg halted fibrosis progression in the CDAHFD model. Conclusion: EDP‐305 reduced fibrosis progression in rat BDL and mouse CDAHFD models. Molecular imaging of collagen and oxidized collagen is sensitive to changes in fibrosis and could be used to noninvasively measure treatment response in clinical trials. (Hepatology Communications 2018;2:821‐835)

show abstract

Section: Methodsmentioning

confidence: 99%

Molecular magnetic resonance imaging accurately measures the antifibrotic effect of EDP‐305, a novel farnesoid X receptor agonist

Erstad

Farrar

Ghoshal

et al. 2018

Hepatology Communications

View full text Add to dashboard Cite

show abstract

“…Several comments need to be made regarding Equations [1][2][3]. First, W, F, , and 0 in Equation [1] and ⌬B 0 in Equation [3] are all spatially dependent and thus may vary from pixel to pixel. While changes in ⌬B 0 in principle affect ␣ as well, the magnitude of ⌬B 0 is much smaller than B 0 .…”

Section: Signal Modelmentioning

confidence: 99%

“…In contrast, is determined by the magnetic field inhomogeneity (see Eq. [3]) and, therefore, should be constant for all the coils. Second, W and F are the magnitudes of the water and fat magnetizations at the time of the sampling.…”

Section: Signal Modelmentioning

confidence: 99%

“…Reliable and consistent water/fat separation for an entire image and the success of the two-point Dixon technique are, therefore, affected by the presence of , which in turn is directly related to the magnetic field inhomogeneity (Eq. [3]). Nonetheless, it is interesting to note that by taking the absolute value of the images before summation or subtraction, the water and fat separation is actually already correct on a pixel level without the need to know the actual phase errors.…”

Section: The Original Two-point Dixon Techniquementioning

confidence: 99%

See 1 more Smart Citation

Dixon techniques for water and fat imaging

2008

Magnetic Resonance Imaging

489

435

View full text Add to dashboard Cite

In 1984, Dixon published a first paper on a simple spectroscopic imaging technique for water and fat separation. The technique acquires two separate images with a modified spin echo pulse sequence. One is a conventional spin echo image with water and fat signals in-phase and the other is acquired with the readout gradient slightly shifted so that the water and fat signals are 180°out-of-phase. Dixon showed that from these two images, a water-only image and a fat-only image can be generated. The wateronly image by the Dixon's technique can serve the purpose of fat suppression, an important and widely used imaging option for clinical MRI. Additionally, the availability of both the water-only and fat-only images allows direct imagebased water and fat quantitation. These applications, as well as the potential that the technique can be made highly insensitive to magnetic field inhomogeneity, have generated substantial research interests and efforts from many investigators. As a result, significant improvement to the original technique has been made in the last 2 decades. The following article reviews the underlying physical principles and describes some major technical aspects in the development of these Dixon techniques. MR IMAGES ACQUIRED IN VIVO usually contain signals from both water and fat. In many pulse sequences, fat appears hyperintense. However, the contribution from water is often of the primary interest for many practical applications. Without suppression, the bright fat signal may result in aggravated motion-related artifacts and, more importantly, reduce the underlying lesion conspicuity. Because of its chemical shift, fat is also responsible for the well-known spatial misregistration artifacts, which can appear both along the frequency encode direction and along the slice select direction. For a few other applications such as diagnosis of bone marrow diseases or hepatic steatosis, detection rather than suppression of the fat signal can also be valuable.Several approaches have been proposed and developed for achieving fat suppression. Perhaps the most popular is the chemical shift selective saturation (1) or its variants. In this approach, a frequency selective radiofrequency (RF) pulse and a spoiler gradient pulse are used in conjunction to first excite and then saturate the fat magnetization before water is excited for imaging. Alternatively, a frequency selective RF pulse can be used to directly excite only the water magnetization and leave the fat magnetization alone along the longitudinal axis. These techniques, particularly the selective saturation technique, are easy to implement and have been widely used with great success. However, both selective saturation pulses and selective excitation pulses increase the scan time. Another limitation for fat suppression by the selective saturation pulses is that it typically requires an accurate 90°flip angle, and as a result, its performance can be dependent on B1 homogeneity. Perhaps most importantly, fat suppression using the frequency selective approach...

show abstract

“…These artifacts are similar to the chemical shift artifact of water and lipids in MRI in the readout direction. One approach to separate water and lipids in MRI is to perform at least two experiments with a defined phase shift and afterward to apply a phase-sensitive reconstruction to the data, a method known as "Dixon editing" (20,21).…”

mentioning

confidence: 99%

Sensitive J‐coupled metabolite mapping using Sel‐MQC with selective multi‐spin‐echo readout

Melkus

Mörchel

Behr

et al. 2009

Magnetic Resonance in Med

View full text Add to dashboard Cite

The selective multiple quantum coherence technique is combined with a read gradient to accelerate the measurement of a specific scalar-coupled metabolite. The sensitivities of the localization using pure phase encoding and localization with the read gradient are compared in experiments at high magnetic field strength (17.6 T). Multiple spin-echoes of the selective multiple quantum coherence edited metabolite are acquired using frequency-selective refocusing of the specified molecule group. The frequency-selective refocusing does not affect the J-modulation of a coupled spin system, and the echo time is not limited to a multiple of 1/J to acquire pure in-phase or antiphase signal. The multiple echoes can be used to accelerate the metabolite imaging experiment or to measure the apparent transverse relaxation T 2 . A simple phase-shifting scheme is presented, which enables the suppression of editing artifacts resulting from the multiple spin-echoes of the water resonance. In 1 H NMR spectroscopy, the spectral overlap of resonances is a common problem when information about a specific metabolite (e.g., lactate [Lac]) is desired in vivo. In the last decades, several types of spectral editing schemes were developed to filter the metabolite of interest from coresonant or overlapping signals (1-4). The class of multiple quantum coherence (MQC) filters using magnetic field gradients for editing provides robust single-shot editing techniques. One of the single-shot editing filters is the frequency selective multiple quantum coherence editing scheme (Sel-MQC) proposed by He et al. (5). This selective MQC filter enables editing of a single scalar-coupled spin system with simultaneous suppression of water and other resonances in one scan.Successful applications of the Sel-MQC editing sequence have been shown in several studies in which the metabolite of interest is overlapped by other spins with a similar chemical shift. For instance, in extracranial tumor tissues, the Lac CH 3 resonance (at 1.33 parts per million [ppm]) has been filtered from overlapping methylene groups of mobile lipids (5,6). A recent preliminary study on healthy and cancerous human breast tissue has shown a robust application of the Sel-MQC editing sequence to detect polyunsaturated fatty acids (PUFA) (7). The olefinic methylene protons of PUFA at 5.3 ppm that are coupled with the allylic methylene protons of unsaturated acyl chains at 2.8 ppm were detected in breast tissue, and the PUFA pattern is sensitive to breast tissue changes, including cancerous alterations. An adiabatic version of the Sel-MQC scheme was used by de Graaf et al. (8) to detect the ␤H1-glucose resonance at 4.63 ppm in rat brain in vivo. Executing the Sel-MQC sequence with adiabatic radiofrequency pulses allows optimal sensitivity when surface coils are used. In recent years, several extensions of the Sel-MQC editing scheme have been developed, such as Hadamard encoding for localization (9,10), multislice selection using spatial-spectral selective pulses (11), T 1 and T 2 relaxation ...

show abstract

Simple proton spectroscopic imaging.

Cited by 1,973 publications

References 0 publications

Molecular magnetic resonance imaging accurately measures the antifibrotic effect of EDP‐305, a novel farnesoid X receptor agonist

Molecular magnetic resonance imaging accurately measures the antifibrotic effect of EDP‐305, a novel farnesoid X receptor agonist

Dixon techniques for water and fat imaging

Sensitive J‐coupled metabolite mapping using Sel‐MQC with selective multi‐spin‐echo readout

Contact Info

Product

Resources

About